62 research outputs found
Technological change, campaign spending and polarization
No full textWe present a model of electoral competition with endogenous platforms and campaign spending where the division of voters between impressionable and ideological is also endogenous and depends on parties’ strategic platform choices. Our approach results in a tractable model that provides interesting comparative statics on the effect of recent technological advancements. For instance, we can accommodate a new justification behind the well-documented simultaneous increase in campaign spending and polarization: an increase in the effectiveness of electoral advertising, or a decrease in the electorate’s political awareness, surely increases polarization and may also increase campaign spending
Strategic choice of sharing rules in collective contests
No full textCompetition between groups often involves prizes that have both a public and a private component. The exact nature of the prize not only affects the strategic choice of the sharing rules determining its allocation but also gives rise to an interesting phenomenon not observed when the prize is either purely public or purely private. Indeed, we show that in the two-groups contest, for most degrees of privateness of the prize, the large group uses its sharing rule as a mean to exclude the small group from the competition, a situation called monopolization. Conversely, there is a degree of relative privateness above which the small group, besides being active, even outperforms the large group in terms of winning probabilities, giving rise to the celebrated group size paradox
Linking individual and collective contests through noise level and sharing rules
No full textWe propose the use of Nitzan’s (1991) sharing rule in collective contests as a tractable way of modeling individual contests. This proposal (i) tractably introduces noise in Tullock contests when no closed form solution in pure strategies exists, (ii) satisfies the important property of homogeneity of degree zero, (iii) can be effort or noise equivalent to a standard Tullock contest
Sequential choice of sharing rules in collective contests
No full textGroups competing for a prize need to determine how to distribute it among their members in case of victory. Considering competition between two groups of different size, we show that the small group's sharing rule is a strategic complement to the large group's sharing rule in the sense that if the small group chooses a more meritocratic sharing rule, the large group wishes to choose a more meritocratic rule as well. On the contrary, the large group's sharing rule is a strategic substitute to the small group's sharing rule, hence the timing of choice is crucial. For sufficiently private prizes, a switch from a simultaneous choice to the small group being the leader consists in a Pareto improvement and reduces aggregate effort. On the contrary, when the large group is the leader, aggregate effort increases. As a result, the equilibrium timing is such that the small group chooses its sharing rule first. If the prize is not private enough, the small group retires from the competition and switching from a simultaneous to a sequential timing may reverse the results in terms of aggregate effort. The sequential timing also guarantees that the small group never outperforms the large one
Framing effects on risk-taking behavior: evidence from a field experiment in multiple choice tests
No full textWe exploit testing data to gain better understanding on framing effects on decision-making and performance under risk. In a randomized field experiment, we modified the framing of scoring rules for penalized multiple-choice tests. In penalized multiple-choice tests, right answers are typically framed as gains while wrong answers are framed as losses (Mixed-framing). In the Loss-framing proposed, both non-responses and wrong answers are presented in a loss domain. According to our theoretical model, we expect the change in the framing to decrease students' non-response and to increase students' performance. Under the Loss-framing, students' non-response reduces by a 18%-20%. However, it fails to increase students¿ scores. Indeed, our results support the possibility of impaired performance in the Loss-framing.Pau Balart and Lara Ezquerra acknowledge financial support from Fundación Ramón Areces through the XVII Concurso Nacional para la Adjudicación de Ayudas a la Investigación en Ciencias Sociales. Iñigo Hernandez-Arenaz acknowledges financial support from Ministerio de Ciencia, Innovación y Universidades (PID2019-108343GA-I00)
Effects of Superheat and Solute Additions on the Grain Size in Binary Copper Alloys
No full text© The Author(s) 2019. By utilizing data from the literature, we examine the effects of superheat and solute additions on the grain size (as measured by columnar grain length) in binary copper alloys. Our investigation provides support for an Arrhenius-like behavior of the superheat on the grain size. We also find a correlation between the columnar grain length at a constant degree of superheat and the variation of the reciprocal of the true growth restriction factor (1/Q) with P, Mg, Mn, Pb, and Sn solute additions to be a power of law of 1/3, which gave a better fit than a linear one.EPSRC (UK
Parallel duplication and loss of aquaporin‐coding genes during the “out of the sea” transition as potential key drivers of animal terrestrialization
No full textOne of the most important physiological challenges animals had to overcome during terrestrialization (i.e., the transition from sea to land) was water loss, which alters their osmotic and hydric homeostasis. Aquaporins are a superfamily of membrane water transporters heavily involved in osmoregulatory processes. Their diversity and evolutionary dynamics in most animal lineages remain unknown, hampering our understanding of their role in marine–terrestrial transitions. Here, we interrogated aquaporin gene repertoire evolution across the main terrestrial animal lineages. We annotated aquaporin-coding genes in genomic data from 458 species from seven animal phyla where terrestrialization episodes occurred. We then explored aquaporin gene evolutionary dynamics to assess differences between terrestrial and aquatic species through phylogenomics and phylogenetic comparative methods. Our results revealed parallel aquaporin-coding gene duplications during the ecological transition from marine to nonmarine environments (e.g., brackish, freshwater and terrestrial), rather than from aquatic to terrestrial ones, with some notable duplications in ancient lineages. In contrast, we also recovered a significantly lower number of superaquaporin genes in terrestrial arthropods, suggesting that more efficient oxygen homeostasis in land arthropods might be linked to a reduction in this type of aquaporin. Our results thus indicate that aquaporin-coding gene duplication and loss might have been one of the key steps towards the evolution of osmoregulation across animals, facilitating the “out of the sea” transition and ultimately the colonization of land.Fil: Martínez Redondo, Gemma I.. Consejo Superior de Investigaciones Científicas; EspañaFil: Simón Guerrero, Carolina. Consejo Superior de Investigaciones Científicas; EspañaFil: Arístide, Leandro. Universidad Nacional Arturo Jauretche. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos; ArgentinaFil: Balart García, Pau. Consejo Superior de Investigaciones Científicas; EspañaFil: Tonzo, Vanina. Consejo Superior de Investigaciones Científicas; EspañaFil: Fernández, Rosa. Consejo Superior de Investigaciones Científicas; Españ
Highly dynamic evolution of the chemosensory system driven by gene gain and loss across subterranean beetles
No full textAvailable online 14 February 2024Chemical cues in subterranean habitats differ highly from those on the surface due to the contrasting environmental conditions, such as absolute darkness, high humidity or food scarcity. Subterranean animals underwent changes to their sensory systems to facilitate the perception of essential stimuli for underground lifestyles. Despite representing unique systems to understand biological adaptation, the genomic basis of chemosensation across cave-dwelling species remains unexplored from a macroevolutionary perspective. Here, we explore the evolution of chemoreception in three beetle tribes that underwent at least six independent transitions to the underground, through a phylogenomics spyglass. Our findings suggest that the chemosensory gene repertoire varies dramatically between species. Overall, no parallel changes in the net rate of evolution of chemosensory gene families were detected prior, during, or after the habitat shift among subterranean lineages. Contrarily, we found evidence of lineage-specific changes within surface and subterranean lineages. However, our results reveal key duplications and losses shared between some of the lineages transitioning to the underground, including the loss of sugar receptors and gene duplications of the highly conserved ionotropic receptors IR25a and IR8a, involved in thermal and humidity sensing among other olfactory roles in insects. These duplications were detected both in independent subterranean lineages and their surface relatives, suggesting parallel evolution of these genes across lineages giving rise to cave-dwelling species. Overall, our results shed light on the genomic basis of chemoreception in subterranean beetles and contribute to our understanding of the genomic underpinnings of adaptation to the subterranean lifestyle at a macroevolutionary scale.Pau Balart-García, Tessa M. Bradford, Perry G. Beasley-Hall, Slavko Polak, Steven J. B. Cooper, Rosa Fernánde
Smelling in the dark: Phylogenomic insights into the chemosensory system of a subterranean beetle
No full textThe chemosensory system has experienced relevant changes in subterranean animals, facilitating the perception of specific chemical signals critical to survival in their particular environment. However, the genomic basis of chemoreception in cave-dwelling fauna has been largely unexplored. We generated de novo transcriptomes for antennae and body samples of the troglobitic beetle Speonomus longicornis (whose characters suggest an extreme adaptation to a deep subterranean environment) in order to investigate the evolutionary origin and diversification of the chemosensory gene repertoire across coleopterans through a phylogenomic approach. Our results suggested a diminished diversity of odourant and gustatory gene repertoires compared to polyphagous beetles that inhabit surface habitats. Moreover, S. longicornis showed a large diversity of odourant-binding proteins, suggesting an important role of these proteins in capturing airborne chemical cues. We identified a gene duplication of the ionotropic coreceptor IR25a, a highly conserved single-copy gene in protostomes involved in thermal and humidity sensing. In addition, no homologous genes to sugar receptors or the ionotropic receptor IR41a were detected. Our findings suggest that the chemosensory gene repertoire of this cave beetle may result from adaptation to the highly specific ecological niche it occupies, and that gene duplication and loss may have played an important role in the evolution of gene families involved in chemoreception. Altogether, our results shed light on the genomic basis of chemoreception in a cave-dwelling invertebrate and pave the road towards understanding the genomic underpinnings of adaptation to the subterranean lifestyle at a deeper level.This work was supported by the Ministerio de Economía y Competitividad and the Ministerio de Ciencia of Spain (CGL2016-76705-P to Ignacio Ribera, PID2019-108824GA-I00 to Rosa Fernández, and CGL2016-75255 and PID2019-103947GB to Julio Rozas). Pau Balart-García and Paula Escuer were supported by an FPI grant (Ministerio de Economía y Competitividad BES-2017-081050 and BES-2017-081740, respectively). Rosa Fernández was supported by a Marie Sklodowska-Curie grant (747607) and a Ramón y Cajal fellowship (Ministerio de Economía y Competitividad, RyC2017-22492).Peer reviewe
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